A DRAM includes a transistor and a capacitor in one cell. A source region and a drain region of the transistor are provided in a semiconductor substrate, and the capacitor is electrically coupled to the drain region of the transistor. Whether the one cell is turned on or off is determined by whether an electric charge is accumulated in the capacitor.
The electric charge accumulated in the capacitor is leaked (discharged) with the passage of time. When the electric charge accumulated in the capacitor reaches a predetermined value or less, an error occurs. Hence, the DRAM performs a so-called refresh operation. The refresh operation may be performed several tens of times per second, for example. In order to reduce the number of times of the refresh operation per unit time, namely, in order to improve retention characteristics, hydrogen sintering is performed in manufacturing of the DRAM. The hydrogen sintering is heat treatment in an atmosphere containing hydrogen, and is performed near a final process after forming an insulating film, wiring, and other components on a semiconductor substrate (for example, refer to Patent Literature 1). Hydrogen sintering treatment may be executed also in manufacturing of semiconductor devices such as solid-state imaging devices and logic devices in addition to the DRAM.